Vacuum skin packaging method

ABSTRACT

A method of packaging an article between at least two package members, such as plastic film in web form, is provided, including the steps of pushing one such member around the article and closely adjacent the other member, followed by partial, then full, sealing of opposed parts of these members together. Specifically a method of forming a vacuum skin package is provided including the steps of: POSITIONING AN ARTICLE TO BE PACKAGED BETWEEN A TOP AND BOTTOM WEB OF PLASTIC FILM, WITH THE BOTTOM PART OF THE ARTICLE RESTING ON THE BOTTOM WEB; PUSHING, BY MEANS OF WEB POSITIONING MEANS, THE TOP WEB INTO A FIRST PACKAGE FORMING POSITION WHEREAT SUCH TOP WEB IS IN CONTACT WITH THE TOP PART OF THE ARTICLE, IS CLOSELY ADJACENT THE SIDE PARTS OF THE ARTICLE, AND IS SPACED FROM AND IS CLOSELY ADJACENT THE BOTTOM WEB; REMOVING AIR FROM BETWEEN THE TOP AND BOTTOM WEBS WHILE THE TOP WEB IS IN THE FIRST PACKAGE FORMING POSITION; MOVING, BY MEANS OF WEB POSITIONING MEANS, THE TOP AND BOTTOM WEBS RELATIVE TO EACH OTHER AND INTO A SECOND PACKAGE FORMING POSITION WHEREAT SPACED PARTS OF THE TOP WEB ARE IN SEALING CONTACT WITH OPPOSED PARTS OF THE BOTTOM WEB, STILL LEAVING OTHER SPACED, OPPOSED PARTS OF THE TOP AND BOTTOM WEB UNSEALED; AND PUSHING, BY MEANS OF AIR EXERTED ON THE OUTER SURFACE OF THE TOP WEB, THE TOP WEB INTO A THIRD PACKAGE FORMING POSITION, WHEREAT SUCH OTHER SPACED, OPPOSED PARTS OF THE TOP AND BOTTOM WEBS ARE IN SEALING CONTACT AND OTHER PARTS OF THE TOP WEB ARE IN SKINLIKE CONTACT WITH THE TOP AND SIDE PARTS OF THE ARTICLE THEREBY TO FORM A SEALED VACUUM SKIN PACKAGE.

Unite at Ramsey atent [1 States VACUUM SKIN PACKAGING METHOD [75] Inventor: Harold Eugene Ramsey,

Wilmington, Del.

[73] Assignee: E. l. du Pont de Nemours & Company, Wilmington, Del.

[22] Filed: Oct. 17, 1973 [21] Appl. No.: 407,249

[52] US. Cl 53/22 A [51] Int. Cl B65b 31/02 [58] Field of Search 53/22 A, 112 A {56] References Cited UNITED STATES PATENTS 3,260,032 7/1966 Hill et al. 53/112 A 3,634,993 l/l972 Pasco et al 53/22 A Primary Examiner-Travis S. McGehee 57 ABSTRACT A method of packaging an article between at least two package members, such as plastic film in web form, is provided, including the steps of pushing one such member around the article and closely adjacent the other member, followed by partial, then full, sealing of opposed parts of these members together.

Specifically a method of forming a vacuum skin package is provided including the steps of:

positioning an article to be packaged between a top and bottom web of plastic film, with the bottom part of the article resting on the bottom web;

pushing, by means of web positioning means, the top web into a first package forming position whereat suchtop web is in contact with the top part of the article, is closely adjacent the side parts of the article, and is spaced from and is closely adjacent the bottom web;

removing air from between the top and bottom webs while the top web is in the first package forming position;

moving, by means of web positioning means, the top and bottom webs relative to each other and into a second package forming position whereat spaced parts of the top web are in sealing contact with opposed parts of the bottom web, still leaving other spaced, opposed parts of the top and bottom web unsealed; and

pushing, by means of air exerted on the outer surface of the top web, the top web into a third package forming position, whereat such other spaced, opposed parts of the top and bottom webs are in sealing contact and other parts of the top web are in skin-like contact with the top and side parts of the article thereby to form a sealed vacuum skin package.

1 Claim, 5 Drawing Figures PATENTEDJUN 24 ms v SHEET VACUUM SKIN PACKAGING METHOD BACKGROUND OF THE INVENTION 1. Field of the Invention This invention is a package-making method and, more particularly, is directed to a novel method of skin packaging an article or a plurality of articles in plastic film.

More specifically, the invention relates to a method of packaging a high profile article, such as a piece of meat, in plastic film to form a skin package including the steps of pushing or moving, in three distinct stages, a top plastic web around and into skin-like engagement with the article being packaged and into partial, then full, sealing engagement with a bottom plastic web carrying the article by means of web positioning means,. followed by air pressure.

2. Description of the Prior Art Packaging methods of this general type are old. It is known, for example, to skin package an article by pushing a top web into engagement with an article and a bottom web by exerting air pressure on the top web, for example.

U.S. Pat. No. 2,690,593 to Abercrombie, which is exemplary of the prior art, discloses moving a heater housing and platen towards a base to envelop an article positioned thereon in a plastic sheet, followed by subjecting the surface of the plastic sheet to reduced pressure to shrink it about the article.

U.S. Pat. No. 2,799,589 to Grinstead discloses placing a product within packaging material, the edges of which are clamped to produce a fluid tight joint, after which a greater pressure is applied to the outer surface of the material than that existing on the inner surface of the material.

U.S. Pat. No. 3,290,858 to Eberman et al. discloses a continuous package-forming machine in which vacuum means are provided for holding an upper film out of the way of an article to define an article-receiving pocket therefor, followed by shrinking the upper film about the article and into sealing contact with a lower film in a continuous operation.

U.S. Pat. No. 3,491,504 to Young et al. teaches a method and apparatus for vacuum skin packaging in which a heated upper film is draped over the product while preventing premature sealing of it to a lower packaging member while air is removed between the film and the packaging member, after which the film is pushed against the product against the package member to form a heat-sealed skin packaged product.

U.S. Pat. No. 3,694,991 to Perdue et al. discloses a vacuum skin package, and process and apparatus for making the same. In this patent a flexible sheet is shaped into a cavity then positioned over the product and out of contact with it, after which the space between the sheet and a bottom supporting member is evacuated. The sheet is then moved from its concave shape and into the product and into sealing contact with the supporting member.

Other patents of interest include U.S. Pat, No. 2,918,767 to Grinstead et al. and No. 3,195,288 to Sloan et al.

These patents teach apparatus methods that are generally effective in packaging low profile articles; problems, however, often result when packaging high profile articles using such methods and apparatus in that the seals fail due to fins or capillaries formed in the top web during the package-making operation. By carefully controlling the pushing or positioning of the top web over and around the article being packaged and, hence, into partial, then full, sealing contact with opposed parts of the bottom web, the formation of these fins and capillaries is avoided and improvements are realized in packaging high profile articles (and also low profile articles where similar problems exist) by following the the teachings of this invention.

SUMMARY OF THE INVENTION Briefly described, a method of forming of vacuum skin package of this invention includes the steps of:

positioning an article to be packaged between a top and bottom web of plastic film, with the bottom part of the article resting on the bottom web;

pushing the top web into a first package forming position by means of web positioning means into and around the article and toward such bottom web whereat such top web is in contact with the top part of the article and is closely adjacent all the side parts of the article and is spaced from and closely adjacent the bottom web;

removing air from between the top and bottom web while the top web is in its first package forming position; moving the top and bottom webs relative to each other and into a second package forming position by means of the web positioning means whereat opposed parts of such top web are in sealing contact with parts of the bottom web, still leaving other parts of the top and bottom webs unsealed;

pushing the other parts of top web into a third package forming position by means of air exerted on the outer surface of the top web whereat the other opposed parts of the top web are in sealing contact with the bottom web to complete sealing of the package and other parts of the top web are in skinlike contact with the top and side parts of the article thereby to form a sealed skin-package.

This invention specifically improves a packaging method of the type taught in U.S. Pat. No. 3,491,504 to Young et al., for example.

It was found, particularly when packaging high profile articles, when using such a method that there was a tendency for fins or capillaries to form during the packaging operation and that air tended to leak back into the package because portions of these fins or capillaries were not effectively sealed together. Such fins may result due to the product or article height or could result due to the shape, arrangement or location of the article within the vacuum chamber. As an example, when packaging a high profile article using the Young et al. method, a triangular shaped tenting of the upper web often results extending from the four corners of the vacuum chamber to the apex of the high profile article. This, of course, results in four pronounced fins radiating to each corner of the chamber and miscellaneous smaller fins or capillaries and, as a result, hermetic seals are not maintained in certain instances because of leakage of air into the passageways associated with the fins. As a result of this leakage, the utility of vacuum packages, where this problem has occurred, is destroyed.

In the instant invention web positioning means are used to diminish the potential of fins or capillaries occurring during the package forming operation. This also greatly reduces the size of the fins formed around the product and results in the package having greater seal integrity. This solution to the problems as discussed previously greatly improves methods of the Young et al. type and has rendered the making of a sealed vacuum skin package even in cases where high profile and unusually shaped articles are packaged, a capability now available to the art and such capability is this invention.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a partial schematic sectional view of an apparatus capable of performing the packaging method of this invention;

FIG. 2 is a schematic sectional view of a vacuum chamber (in open position) of the apparatus of FIG. 1 showing an article on a bottom web, with a top web draped or positioned over the top part of the article but not in close proximity with all the side parts of the article;

FIG. 3 is a schematic sectional view of the vacuum chamber of FIG. 2 in its closed position showing the top web pushed around and in close proximity with all the side parts of the article but spaced from the bottom web;

FIG. 4 is a planar sectional view taken along line 44 of FIG. 3, immediately after air is removed from between the top and bottom webs and the webs are moved adjacent to each other into the second package forming position, showing spaced partial seals of the top web to opposed parts of the bottom web around the article being packaged; and

FIG. 5 is a schematic sectional view of the vacuum chamber of FIG. 2 in its closed position after the unsealed parts of the top web have been pushed into full sealing contact with opposed parts of the bottom web and after other parts of the top web have been pushed into skin-like engagement with the top and side parts of the article thereby to form a vacuum skin package.

DESCRIPTION OF THE PREFERRED EMBODIMENT An apparatus for performing the packaging method of this invention is schematically shown in FIG. 1, which method is an improvement over vacuum packaging methods of the types known to the prior art, such as those shown in U.S. Pats. Nos. 3,491,504 and 3,694,991, for example.

In such prior art methods of vacuum packaging, a product is positioned on a bottom heat-scalable web within a vacuum chamber and a heat-sealable top web is positioned over the product. The space surrounding the product between the top and bottom webs is evacuated and the top web is driven onto the product and into contact with the bottom web in a vacuum-sealing relationship.

The problem with these, and similar, methods has been the formation of fins, which cause package leaks, particularly when packaging high profile articles. The method of this invention solves this problem.

Referring to the drawing, the improved method of this invention of forming a vacuum skin package includes the steps of:

positioning an article A to be packaged between a top web 1 and a bottom web 2 of plastic film, with the bottom part of the article resting on the bottom web; pushing, by means of web positioning means 3, the top web 1 into a first package forming position whereat such top web 1 is in contact with the top part of the article A, is closely adjacent all the side parts of the article, and is spaced from and is closely adjacent the bottom web 2;

removing air from between the top and bottom webs l and 2 while the top web 1 is in the first package forming position; moving, by means of the web positioning means 3, the top and bottom webs 1 and 2 relative to each other and into a second package forming position whereat spaced parts of the top web 1 are in sealing contact with opposed parts of the bottom web 2 still leaving other spaced, opposed parts of the top and bottom web unsealed; and pushing, by means of air exerted on the outer surface of the top web 2, the top web into a third package forming position, whereat such other spaced, opposed parts of the top and bottom webs are in sealing contact and other parts of the top web are in skin-like contact with the top and side parts of the article A thereby to form a sealed vacuum skinpackage P. With further reference to the drawing, the improvement of the packaging method of this invention over prior art methods, in great detail, essentially comprises: heating the heat-sealable top web 1 to a heat-forming temperature by using a heater 5;

positioning a section of the top web 1 over the article A that is prepositioned on a section of the bottom heat-sealable web 2;

passing the section of web 1, the article A and the section of the bottom web 2 within a vacuum chamber 6;

preforming the top web 1 around the positioned article A so that the web 1 completely surrounds and is in intimate contact with the upper portion of the article and otherwise completely surrounds the article;

evacuating the space between the top web 1 and the bottom web 2 that surrounds the article so that the air follows the path of the arrows shown in FIG. 3 around the edge of the bottom web 2 into the lower portion of the vacuum chamber 6 and out an exhaust port;

sealing portions of the top web 1 to corresponding portions of the bottom web 2 in spaced zones 4 around the positioned product A; and

causing the top web 1 by use of differential air pressure to be driven into an intimate heat-sealing engagement with the bottom web 2 around the confines of the article A in the remaining unsealed areas surrounding the sealed spaced zones.

FIG. 2 shows in greater detail the vacuum chamber 6 in its initial opened position. The top web 1 can be predraped, as shown, over the article A or can be free of the article A as it arrives at the vacuum chamber 6 and in a position substantially parallel with the bottom web 2 but completely clear of'the article A. In either configuration of the top web 1 it is in a position favorable to being acted on by sealing ring 7 supported from the vacuum chamber by arms 8. The sealing ring 7, which has a discontinuous lower surface for contacting the top web, extends below the vacuum chamber seal 9 when in the open position as shown in FIG. 2 and is spring-loaded by springs and 11. The upper portion of the vacuum chamber is evacuated and pressurized by use of an exhaust port 12 and the lower portion of the vacuum chamber is evacuated and pressurized by use of an exhaust port 13. Elevator platform 14 is operable in the vertical direction by actuating its support rod 15. This platform is used to assist in effecting the intermittent seals between the top web 1 and bottom web 2 by exerting pressure on the bottom web 2 during the intermittent sealing operation. It is also used to facilitate the removal of the finished package from the vacuum chamber 6.

FIG. 3 shows the vacuum chamber 6 in its closed position whereby air may be evacuated from within the package being formed and from within the vacuum chamber 6. The bottom web 2 is shown positioned on the elevator platform 14 while the web 1 is shown secured between the sections of the vacuum chamber 6 and forming a tight seal with vacuum chamber seal 9. The sealing ring 7 has depressed the web 1 around the product and into its first package forming position.

FIG. 4 shows in detail a discontinuously sealed peripheral path around the product A caused by the spring-loaded action of the sealing ring 7 and the further upward movement of the platform 14. The sealing ring 7 and platform 14 comprise essential parts of the web positioning means 3 and push and/or move the top and bottom webs 1 and 2 relative to each other and into their first and second package forming positions. As shown in FIG. 4, in the second package forming position the top web 1 is sealed to the bottom web 2 preferably at spaced, opposed parts thereof. This permits any remaining air entrapped around the article A to be evacuated along paths such as 18 and 19 if required, but, more importantly, this partial sealing of the webs together prevents the formation of unsightly fins extending from the overwrapped article A to the edges of the finished package during the final package forming step when differential pressure across the web 1 within the vacuum chamber 6 forces the top web 1 to be sealed with the bottom web 2 in a skin-tight configuration around article A. This results in a very tight skin package as shown in FIG. 5 with all the contour of the article intimately enveloped by the top web 1 and without evidence of excess web in the form of fins surrounding the packaging product.

It is important to obtain good initial contact between the top web 1 and the bottom web 2 in the second package forming position. This contact may be enhanced by the use of the spring biased sealing ring 7 and the platform 14 as has been explained. It is important to note that by establishing this contact, tenting is dramatically reduced and, in so doing, the amount of air entrapped is reduced, whereby the final sealing requirements are considerably lessened.

It is particularly difficult to effectively skin package high-profile articles because the increased distance between the top and bottom packaging members or webs 1 and 2 creates excessive tenting (the presence of air between the web produces a ballooning effect) and increases the time it takes the top web 1 to reach the bottom web 2 during the package-forming operation.

In known prior art methods, due to tenting some air often remains and prevents the top web 1 from being brought into skin-like engagement with the article A, hence, creating undesirable wrinkles and leakage in the formed package. Further, in packaging high-profile articles, it is difficult to evacuate the package effectively and the air pockets that remain adversely affect package appearance. This invention solves these problems of packaging high-profile articles A by bringing the top and bottom webs 1 and 2 into three distinct package forming positions, as previously described.

In brief summary, this invention is a method of making a vacuum skin package in which a top film l is positioned over an article product A placed on a bottom film 2, which top and bottom films are heat-sealed together after a vacuum is placed upon the product A, the improvement which includes the steps of:

bringing a spring-biased top web pushing and partial sealing means 3 contained within and of lesser diameter than an upper sealing chamber against the upper surface of the top film 1 whereby to push such film snuggly around the product A and to partially seal opposed portions the top film 1 to the bottom film 2, still leaving unsealed portions and pushing the top film 1 against the product A and against the bottom film 2 to seal the unsealed portions of the top film and the bottom film together to form a heat-sealed skin package.

I claim:

1. A method of forming a vacuum skin package is provided including the steps of:

positioning an article to be packaged between a top and bottom web of plastic film, with the bottom part of the article resting on the bottom web;

pushing, by means of web positioning means, the top web into a first package forming position whereat such top web is in contact with the top part of the article, is closely adjacent all the side parts of the article, and is spaced from and is closely adjacent but not sealed to the bottom web;

removing air from between the top and bottom webs while the top web is in the first package forming position;

moving, by means of web positioning means, the top and bottom webs relative to each other and into a second package forming position whereat spaced parts of the top web are in sealing contact with opposed parts of the bottom web, still leaving other spaced, opposed parts of the top and bottom web unsealed; and

pushing, by means of air exerted on the outer surface of the top web, the top web into a third package forming position, whereat such other spaced, opposed parts of the top and bottom webs are in sealing contact and other parts of the top web are in skin-like contact with the top and side parts of the article thereby to form a sealed vacuum skinpackage. 

1. A method of forming a vacuum skin package is provided including the steps of: positioning an article to be packaged between a top and bottom web of plastic film, with the bottom part of the article resting on the bottom web; pushing, by means of web positioning means, the top web into a first package forming position whereat such top web is in contact with the top part of the article, is closely adjacent all the side parts of the article, and is spaced from and is closely adjacent but not sEaled to the bottom web; removing air from between the top and bottom webs while the top web is in the first package forming position; moving, by means of web positioning means, the top and bottom webs relative to each other and into a second package forming position whereat spaced parts of the top web are in sealing contact with opposed parts of the bottom web, still leaving other spaced, opposed parts of the top and bottom web unsealed; and pushing, by means of air exerted on the outer surface of the top web, the top web into a third package forming position, whereat such other spaced, opposed parts of the top and bottom webs are in sealing contact and other parts of the top web are in skinlike contact with the top and side parts of the article thereby to form a sealed vacuum skin-package. 